JPH02186861A - Data communication equipment - Google Patents

Abstract

PURPOSE:To efficiently perform communication by using a character synchronizing system when specific terminal equipment is selected by a host computer, and using a stepping synchronizing system after establishing a data link obtained as a result. CONSTITUTION:When polling is performed by selecting terminal equipment with a specific address, for example, the terminal equipment 10, by the host computer 1 that is a control station, the character synchronizing system which takes synchronization with a certain decided bit pattern of communication data is used, and an interruption processing is performed at the terminal equipment 10 side by detecting a specific bit pattern decided at every terminal equipment in a hardware manner. And after the data link is established by performing the polling, data communication is performed at every data regardless of the direction of transmission/reception data by the steeping synchronizing system in which the synchronization is taken by a start bit and a stop bit. In such a way, the data communication can efficiently be performed by reducing a load in the communication.

Description

[Detailed Description of the Invention] [Industrial Application Field 1] The present invention relates to a data communication device that exchanges data between a host computer that is a control station and two or more terminal devices that are dependent stations. be.

[Summary of the Invention 1 This invention provides an RS422 I/F from a host computer.
A data communication device that uses a polling/selecting method from a host computer to perform data communication between two or more terminal devices that are multi-drop connected on a signal line. When selecting and polling a terminal device,
A character synchronization method is used to synchronize communication data using a certain fixed bit pattern, and after the resulting data link is established, an asynchronous method is used to synchronize the start bit and stop bit. This allows pig communications to be performed while reducing the processing load on the host computer and terminal device.

[Conventional technology]

Conventionally, in a data communication system using a polling/selecting method, a specific value of communication data is determined in advance for each terminal device as an address code for selecting the terminal device using an asynchronous method, and the data link is Before the terminal device is established, it constantly monitors the received data, and when it detects its own address code, it establishes a data link and performs data communication, and the character synchronization method allows the terminal device to communicate with the specified information predetermined for each terminal device. There was a method in which the bit pattern of the data was detected using hardware, and after establishing a data link, data communication was performed bit by bit in a time-sharing manner.

[Problem to be Solved by the Invention 1] However, in the conventional asynchronous system, the terminal device constantly monitors whether or not the received data contains its own address code before establishing the data link. This has the drawback that the processing capacity of other terminal devices is reduced due to the load on the terminal device.Also, in the character synchronous method, data communication is performed continuously in a time-sharing manner after the data link is established.
The sending side needs to set the next transmission data within the time-sharing time, and the receiving side also needs to read the next received data within the time-sharing time, and if it cannot be processed within the time, synchronization will be lost and transmission and reception will be delayed. Each time the host computer becomes unavailable or the direction of data transmission and reception changes, it is necessary to establish a data link using a bit pattern for character synchronization, and several bytes of data are sent back and forth between the host computer and the terminal device many times. In this case, there was a drawback that communication efficiency decreased.

Therefore, in this invention, in order to solve these conventional drawbacks, the terminal device that is not polled by the host computer can concentrate on processing other than communication processing,
Data communication between the host computer and the terminal device, which has been polled and a data link has been established, is related to the direction of data transmission and reception (the purpose is to be efficient).

[Means for Solving the Problems] In order to solve the above problems, the present invention provides that when a host computer serving as a control station selects and polls a terminal device with a specific address, Using a character synchronization method that synchronizes using bit patterns, the terminal device side detects a specific bit pattern determined for each terminal device using hardware and processes an interrupt, and the data link is established by the above polling. After that, data communication is efficiently carried out for each piece of data, regardless of the direction of the transmitted and received data, using the start-stop synchronization method that synchronizes with a start bit and a stop bit.

[Effect 1] In the communication system described above, the terminal device before being polled by the host computer not only has increased processing capacity because it can concentrate on processing other than communication processing, but also the data link is The established data communication between the host computer and the terminal device is an asynchronous method, so even if several bytes of data are sent back and forth between the host computer and the terminal device many times, it is necessary to establish a data link each time the direction of the data changes. This reduces the communication load and makes data communication more efficient.

[Example] Hereinafter, an example of the present invention will be described based on the drawings. In the block diagram of the present invention shown in FIG. 2, a host computer 1 includes a CPU 2 and a communication controller 3/RS.
4221/F4, and the CPU 2 and communication controller 3 are connected by a parallel data line 5. The terminal device AIO is connected to the CPU AII and the communication controller A12.
, RS422 I/F 13, and the CPU II and communication controller 12 are connected by a parallel data line 14 and an interrupt control line 15. Terminal device A is R34
Multi-drop connected to 21 on 22 signal line, R342
Two or more terminal devices such as the terminal device AIO and the terminal device 820 are connected to the signal line 21. The communication controller 3 and the communication controller A12 are connected to the parallel data line 5 and the parallel data line 14. It converts into an asynchronous or character synchronous serial signal, and the setting of the asynchronous mode and character synchronous mode is carried out by 0 communication from the CPU2 or CPUAl1 via the parallel data line 5 or the parallel data line 14, respectively. When receiving the character synchronization mode, the controller A12 hardware-wise detects the bit pattern for character synchronization set in advance by the CPU A II, and issues an interrupt control #! 15 can output a signal to CPUAl1.

The operation of the configuration of the present invention will be described with reference to the flowchart shown in FIG. Communication controller 3 of host computer 1 and communication controller AI 2 of terminal device 10
Set each to character synchronization mode, 31.32. A bit pattern 34 for character synchronization is transmitted from the host computer 1 by polling 33.It is converted into serial data by the communication controller 3 and sent from R3422I/F4 to R.
R342 of the terminal device AIO via the 3422 signal line 21
The character synchronization data received by the 2 I/F 13 is detected by the communication controller A12 in terms of hardware, and the 1 communication controller A12 uses the interrupt control 11i.
115 is turned on and the information is transmitted to CPUAl1. CPUA
In l1, when the 1 interrupt control line 15 is turned on, an interrupt occurs 35, and at this point a data link is established 36. After establishing the data link, the communication controller 3 of the host computer 1 and the communication controller A 12 of the terminal device 10 are each set to a start-stop synchronization type (37, 38), and data communications 43 such as commands 39, responses 40, inquiries 41, and requests 42 are performed. When the pig communication 43 is completed, the host computer 1 and the terminal device AIO each perform line termination processing 44 and 45, and one line is terminated by the host computer 1.
The terminal device AIO sends an acknowledgment 47, closes the line, and ends the process.

[Effects of the Invention] As explained above, in a data communication system configured with a plurality of terminal devices connected to a host combinator in a multi-drop manner, when a specific terminal device is selected from a host computer, the present invention uses a character By using the synchronous method and, after establishing the resulting data link, using the start-stop synchronization method, it is effective to reduce the processing load on the host computer and the terminal device and to perform one communication efficiently.

[Brief explanation of the drawing]

FIG. 1 is a flowchart showing the operation of a processing procedure of a data communication device according to the present invention, and FIG. 2 is a block diagram showing the configuration of the data communication device according to the present invention.・Host computer ・Terminal device A ・Polling ・Data link establishment ・Data communication 18'8J process

Claims (1)

[Claims] Consisting of a host computer, a signal line that uses RS422 I/F to transmit data sent and received by the host computer, and two or more terminal devices that are multi-drop connected to the signal line and each have a unique address, In a data communication control system using a polling/selecting method having a first state in which a host computer selects and polls a specific address of a terminal device, and a second state obtained as a result after establishing a data link. , the character synchronization method is used in the first state,
A data communication device characterized in that data communication is performed using an asynchronous method in the second state.